That was the maximum range of Federation Transporters as of the TNG era.Around 40,000 kilometers is the maximum range of transporters. A large chain of ships wouldn't get them out of the system, let alone to a distant world.
Not a bad idea, but there are nowhere near enough ships to do that.
We actually don't know the current range of Federation Transporters, though given they have had decades to study Dominion one's, a safe assumption would be "longer".